This invention relates to partially protected novel trisphenols and a process for production thereof. More particularly, the invention relates to partially protected trisphenols in which only specifically selected one or two of the three hydroxyl groups are protected with a protecting agent and which are suitable for use as a dissolution inhibitor in chemically amplified photoresists and a process for the production of such specifically partially protected trisphenols.
The invention further relates to novel alkoxycarbonylmethoxybenzaldehydes useful as raw materials for the production of monoalkoxycarbonylmethyl ethers of trisphenols, as one of the above-mentioned partially protected trisphenols, wherein one of the hydroxyl groups of the trisphenols is protected with an alkoxycarbonylmethyl group.
It is widely known to micro-fabricate semiconductors by using positive photoresists. In recent years, integrated circuits are more and more integrated and such ultrafine pattern fabrication is needed wherein lines have a width of a half micron or less for the production of VLSI (very large scale integrated) semiconductor circuits. To acchieve such a high resolution, the wavelength of radiation for use in photolithography is more and more shortened, and at present, investigation for practical use of even far ultraviolet rays or excimer laser rays (such as XeCl, KrF or ArF) are carried out.
However, when a conventional positive photoresist comprising a novolak resin and a naphthoquinone diazide compound is used for pattern formation in the photolithography using far ultraviolet rays or excimer laser rays, the rays can hardly reach the bottom of the photoresist layer due to the strong absorption of the novolak resin and naphthoquinone diazide in the far ultraviolet and excimer laser radiation region. As results, fine and accurate patters cannot be formed.
To overcome this problem, a chemically amplified resist composition is proposed. Two component positive photoresist and three component positive photoresist are known as the chemically amplified resist composition. For example, the three component positive photoresist comprises a photoresist composed of a compound which generates an acid (acid generator) upon exposure to radiation and an alkalisoluble polymer (base polymer) such as poly(p-hydroxystyrene) combined with a so-called acid-decomposable dissolution inhibitor. When a layer of the three component positive photoresist is exposed to far ultraviolet rays or excimer laser rays, the acid generator generates an acid in the exposed area and then the reaction of the dissolution inhibitor is caused by making use of the acid as a catalyst. Thus, the solubility of the photoresist is increased in an alkaline developer only in the exposed area so that a positive pattern with high contrast is formed.
As the basic requisites, the acid-decomposable dissolution inhibitor should be permeable (or transparent) to radiation such as far ultraviolet rays or excimer laser rays and compatible with solvents of photoresists or base polymers, and in addition, it should have resistance to etching at pattern portions when being developed. However, no such dissolution inhibitor as to fulfil all the requisites has been known heretofore.
After intensive investigations to solve the problems involved in the known chemically amplified photoresist compositions, the present inventors have found that partially protected trisphenols in which only one or two of the three hydroxyl groups of the trisphenols are protected fulfil all the above-mentioned requisites, and thus completed the invention.
Accordingly, it is an object of the invention to provide a partially protected trisphenol suitable for use as an acid-decomposable dissolution inhibitor in the chemically amplified photoresist compositions.
Furthermore, the etherification of hydroxyl group of trisphenol is hitherto effected by a condensation reaction of the trisphenol with a haloacetic acid ester. However, according to this method, it is not possible to etherify selectively a specific one of the three hydroxyl groups of the trisphenol. For example, if one third molar part of etherification agent is used per molar part of trisphenol, it is not possible to etherify selectively only a specific one of the three hydroxyl groups of the trisphenol.
The inventors have further found that the hydroxyl group of a hydroxybenzaldehyde is first benzyl-etherificated and is then condensed with a phenol, thereby providing a trisphenol in which a specifically selected hydroxyl group only is benzyl-etherificated, and that after protecting the remaining two hydroxyl groups with a protecting agent, the benzyl ether is subjected to hydrogenolysis, thereby readily providing a trisphenol in which only specifically selected two of the hydroxyl groups of the trisphenol are protected with a protecting agent.
Therefore, the invention provides, as a first aspect, a process for the production of partially protected trisphenols wherein specifically selected two hydroxyl groups only are protected with a protecting agent.
The inventors have still further found that a hydroxybenzaldehyde is first protected at its hydroxyl group, for example, as an alkoxycarbonylmethyl ether, and is then condensed with a phenol, thereby readily providing a monoalkoxycarbonylmethyl ether of trisphenol in which only one specifically selected hydroxyl group of the trisphenol is etherificated.
Therefore, the invention provides, as a second aspect, a process for the production of the above-mentioned monoalkoxycarbonylmethyl ether of trisphenol.
Furthermore, the invention provides, as a third aspect, an alkoxycarbonylmethoxybenzaldehyde, a novel compound, useful as a raw material for the production of the above-mentioned monoalkoxycarbonylmethyl ether of trisphenol.
The invention provides a partially protected trisphenol having the general formula (I) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons, X1 is a hydrogen atom, an alkoxycarbonylmethyl group wherein the alkyl group has 1-4 carbons, an alkoxycarbonyl group wherein the alkyl group has 1-4 carbons or a tetrahydropyranyl group, X2 is a hydrogen atom, an alkoxycarbonylmethyl group wherein the alkyl group has 1-4 carbons, an alkoxycarbonyl group wherein the alkyl group has 1-4 carbons or a tetrahydropyranyl group, provided that when X1 is a hydrogen atom, X2 is not a hydrogen atom, and when X2 is a hydrogen atom, X1 is not a hydrogen atom; and m is an integer of 0, 1 or 2, and n is an integer of 0, 1, 2 or 3.
Namely, the invention provides a first partially protected trisphenol having the general formula (Ia) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons, X1 is an alkoxycarbonylmethyl group wherein the alkyl group has 1-4 carbons, an alkoxycarbonyl group wherein the alkyl group has 1-4 carbons or a tetrahydropyranyl group; and m is an integer of 0, 1 or 2, and n is an integer of 0, 1, 2 or 3.
According to the invention, the first partially protected trisphenol having the general formula (Ia) is obtained by a process which comprises:
the first step wherein a hydroxybenzaldehyde having the general formula (II) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons; and m is an integer of 0, 1 or 2, and when m is 2, R1""s may be the same or different from each other, is reacted with a benzyl halide in the presence of an alkali, to prepare a benzyloxybenzaldehyde having the general formula (III) 
wherein R1 and m are the same as hereinbefore defined, and Bz is a benzyl group;
the second step wherein the benzyloxybenzaldehyde is reacted with a phenol having the general formula (IV) 
wherein R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons; and n is an integer of 0, 1, 2 or 3, and when n is 2 or 3, R2""s may be the same or different from each other, in the presence of an acid catalyst, to prepare a monobenzylated trisphenol havingthe general formula (V) 
wherein R1, R2, Bz, m and n are the same as hereinbefore defined;
the third step wherein the monobenzylated trisphenol is reacted with a protecting agent selected from the group consisting of a haloacetic acid alkyl ester wherein the alkyl group has 1-4 carbons, a dialkyl carbonate wherein the alkyl group has 1-4 carbons and 2,3-dihydro-4-H-pyran, thereby protecting two hydroxyl groups in the molecule of the monobenzylated trisphenol, to prepare a trisphenol of which two hydroxyl groups are thus protected and which has the general formula (VI) 
wherein R1, R2, Bz, m and n are the same as hereinbefore defined; and X1 is a protecting group selected from the group consisting of an alkoxycarbonylmethyl group wherein the alkyl group has 1-4 carbons, an alkoxycarbonyl group wherein the alkyl group has 1-4 carbons and a tetrahydropyranyl group; and
the fourth step wherein the trisphenol of which two hydroxyl groups are protected is subjected to hydrogenolysis in the presence of a hydrogenolysis catalyst.
The invention further provides a second partially protected trisphenol having the general formula (Ib) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons, X2 is an alkoxycarbonylmethyl group wherein the alkyl group has 1-4 carbons, an alkoxycarbonyl group wherein the alkyl group has 1-4 carbons or a tetrahydropyranyl group; and m is an integer of 0, 1 or 2, and n is an integer of 0, 1, 2 or 3.
Namely, the invention provides, as the second partially protected trisphenols,
(i) a monoalkoxycarbonylmethoxytrisphenol having the general formula (Ic) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons, R3 is an alkyl group of 1-4 carbons; and m is an integer of 0, 1 or 2, and n is an integer of 0, 1, 2 or 3; or
(ii) a monoalkoxycarbonyloxytrisphenol having the general formula (Id) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons, R3 is an alkyl group of 1-4 carbons; and m is an integer of 0, 1 or 2, and n is an integer of 0, 1, 2 or 3; or
(iii) a monotetrahydropyranyloxytrisphenol having the general formula (Ie) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons; and m is an integer of 0, 1 or 2, and n is an integer of 0, 1, 2 or 3.
According to the invention, the second one of the partially protected trisphenols of the invention is obtained by reacting a benzaldehyde of which hydroxyl group is protected and which has the general formula (VII) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, X2 is an alkoxycarbonylmethyl group wherein the alkyl group has 1-4 carbons, an alkoxycarbonyl group wherein the alkyl group has 1-4 carbons or a tetrahydropyranyl group; and m is an integer of 0, 1 or 2, and when m is 2, R1""s may be the same or different from each other, with a phenol having the general formula (VIII) 
wherein R2 is an alkyl group of 1-6 carbons or a cycloalkyl group of 5 or 6 carbons, R3 is an alkyl group of 1-4 carbons; and n is an integer of 0, 1, 2 or 3, and when n is 2 or 3, R2""s may be the same or different from each other, in the presence of an acid catalyst.
In addition, the invention provides an alkoxycarbonylmethoxybenzaldehyde having the general formula (IX) 
wherein R1 is an alkyl group of 1-4 carbons or an alkoxyl group of 1-4 carbons, R3 is an alkyl group of 1-4 carbons; and m is an integer of 0, 1 or 2, and when m is 2, R1""s may be the same or different from each other.